Electric discharge tube



Dec. 11, 1928 1,695,226

C. BOL

I ELECTRIC DISCHARGE TUBE Filed May 31, 1924 2 Sheets-Sheet l Patented Dec. 11, 1928.

UNITED STATES PATENT OFFICE.

COENELIS 30L,

] EINDHOVEN, NETHERLANDS, ASSIGNOB TO N. V. PHILIPS GLOEI- LLIPEHI'LBRIEKEN, O1? EINDHOVEN, NETHERLANDS.

ELECTRIC DISCHARGE TUBE.

Application illed Kay 8!, i924, Serial No. 717,008, and in the Netherlands June 8, 1923.

This invention relates to improvements in electric discharge tubes and more particularly to the attachment of an incandescent cathode and grid-elcctrmles in electric discharge tubes suitable fora relatively high power.

According to the invention a single glass tube sealed to the wall of the discharge tube is rovided, said tube ending in a number of adacent re-entrant tubes, one or more of which 10 may serve for hermetically attaching a standard carrying a grid-electrode, whereas the others serve for hermetically attaching and introducing the supporting wires for the incandescent cathode.

According to the invention the attachment of the incandescent cathode is preferably effected by hermetically scaling two of the reentrant tubes by means of metal discs or caps, to which the supporting wires for the incandescent wire are secured. In the device according to the-invention it is possible to disposed the incandescent wire and the grid-electrode quite independently from each other, in contradistinction to the usual manner of attaching, according to which the incandescent wire is generally carried not only by its supporting wires but also by the grid. If for example the incandescent cathode consists of a wire which is shaped as a V with a so deep indentation, a metal support may be secured to one of the supporting wires for the incandescent cathode and the bent middle of the incandescent wire may be suspended on the said support and insulated from it. For 5 this purpose the metal support may carry at its end a small tube of quartz or similar insulating material, a small metal rod to which the bent middle of the incandescent cathode is secured being slidable in the said tube.

According to the invention the attachment of a grid may be effected by hermetically sealing a re-cntrant tube by means of a metal disc or cap to which a standard carrying a table is secured. To the said table the support serving for the attachment of a grid-wire are secured.

The device according to the invention is especially applicable to electric discharge tubes, in which an incandescent wire and a grid 50 electrode are for example concentrically arranged within a metal vessel serving as an anode and forming part of the envelope of the tube.

According to the invention the glass tube 5 preferably ends in this case in three re-entrant tubes, the center one of which carries the standard for the grid electrode, whereas the two outer tubes carry the supporting wires for the incandescent wire.

It is advisable to prevent as few electrons as possible from passing out of the open end of the metal vessel. For this purpose the grid may for example be so constructed that it extends some distance outside the anode, and in the portion of the grid outside the anode the turns of the grid wire may be disposed quite closely adjacent each other. According to the invention a simple construction is obtained if a table serving for the attachment of the grid support constitutes a circular surface, the diameter of which corresponds approximately to the interior diameter of the anode. This table closes substantially the open end of the anode excepting for recesses 1n the table which permit the passage of the supports for the other electrodes, and the table is arranged at a slight distance from the end of the anode which leaves an opening around the periphery of the table.

The accompanying drawings represent some constructions of the device according to the invention applied to an electric discharge tube having three electrodes concentrically arranged, the anode being constructed as a metal vessel forming part of the envelope of the tube. In the said drawing;

Figure 1 is a view of a three electrode tube provided with a device according to the invention.

Figure 2 is a view of the arrangement of the incandescent cathode and the grid in the discharge tube shewn in Figure 1.

Figure 3 is a section taken on the line III-III of Figure 2.

Figure 4 is a side view of the lower end of the incandescent wire and its supporting device.

Figure 5' is a view of a different construction of a standard for carrying the grid-electrode, partly in section taken on the line V-V of Figure 6.

Figure 6 IS a bottom view of the latter device.

The discharge tube shewn in Figures 1-4 consists of a hollow metal vessel 2 serving as an anode, to which is fused a glass bulb 1 from the end of which a glass tube 3 extends inwardly. The re-entrant tube 3 ends ,in three adjacent glass tubes 4, 5 and 6 hermetically sealed at their ends by metal discs 7 8 and 9. The leading-in wire 10 is secured to the disc 8 which carries at the other side a metal standard 11 to which a table 12 is fixed.

As material for the vessel 2 and for the discs 7, 8 and 9 any nonporous metallic material may be used which can be readily hermeticallysealed to glass and has preferably the characteristic of liberating as little gas as possible, even if the temperature is raised. For this purpose chrome-iron of suitable composition is preferably used. The disc 8 and the standard 11 may be made in one piece of metal, the standard 11 as well as the table 12 being preferably of chrome-iron.

To the table 12 are secured tour supports 13 (Figure 2) which are mutually held in proper relation to each other by a disc 14 di sosed at the other end. A grid-wire 15 1S Eelically wound on the supports 13. The grid-wire may be of any suitable material for electrodes. If the grid is exposed to comparatively high temperatures such as occur for example in transmission valves of high capacity, the grid wire is preferably of a highly refractory metal such as molybdenum or tungsten. 'The supports 13 may for example be of nickel. If the grid is exposed to high. temperatures, the supports may be of chrome iron, molybdenum, or tungsten. The supports are secured to the table 12 by nuts 16.

In case the supports are of tungsten, such an attachment is not possible, as tungsten can not be threaded, but in this case the manner of attachment by nuts shown in Figures 5 and 6 may be adopted. According to the said figures a solid standard 32 which is integrally connected with a disc 33 intended to be sealed to a glass tube carries a table 34. upports 35 are inserted through apertures 36, and secured to the table 34 by screws 37.

The table 34 as well as the table 12 are disposed adjacent the end of the vessel 2 so that the interior of the said vessel is nearly shut off from the space in the glass vessel 1 and few, if any, of the electrons can leave the vessel 2.

The outermost re-entrant tubes 4 and 6 serve for carrying and hern'ietically introducing the supporting wires for the incandescent Wire. The supporting wires may be introduced across the discs 7 however, they are secured at both sides to the. discs, for example by welding. According to the drawing the discs 7 and 9 have fixed to them leading-in wires and 22 (Figure 1), for example of nickel, and to the latter are fixed wires 21 and 23, for example of copper. Supporting wires 24 and 25 for the incandescent wire are fixed tothe and 9. Preferably other side of the discs and car the two legs of an incandescent wire 26 (i igure 2).

The manner of attachment of the bent end of the incandescent wire is shewn in Figure 3 and F igure 4. A metal support 27 is sccured to the supporting wire 2-1 and carries at its other end a metal clamp 28 which holds a small glass tube 29. In the glass tube a small rod 30 is slidablc and the tip of the incandescent Wire is secured to the said rod in any suitable manner for example by a binding wire 31.

This manner of anchoring the incandescent wire prevents it from sagging and contracting with the grid. The discharge tube is used with the metal vessel 2 downwards. hen the incandescent wire is heated during the operation it expands, and the rod 30 slides slightly downwards in the tube 29, whereas when the incandescent wire cools, the rod 30 is free to move upwards.

The number of the re-entrant glass tubes may of course be altered according to circumstances, also in connection with the number of electrodes to be fixed.

lVhat I claim is:

1. An electric discharge tube comprising a re-entrant glass tube sealed to the wall of the discharge tube, a metal disc or cap-shaped member sealed to and hermetically closing the re-entrant glass tube, a standard attached to said member, a table carried by said standard, a plurality of supports secured to said table, and a wire serving as a grid electrode attached to said supports.

2. An electric discharge tube according to claim 1, comprising a metal vessel serving as an anode and forming part of the envelope of the tube, the table for carrying the grid electrode constituting a substantially imperforate circular surface, said table being dis posed at a slight distance from the end of the anode and being provided with recesses permitting the passage of supports for the other electrodes.

3. An electric discharge tube comprising a re-entrant glass tube sealed to the wall of the discharge tube, a metal disc or cap-shaped member sealed to and hermetically closing the re-cntrantglass tube, a standard attached to said member, a table carried by said standard, holes in said table, a plurality of sup ports secured in said holes, screws to clamp the supports in the holes, and grid wire at tached to said supports.

In testimony whereof I aflix my signature, at the city of Eindhoven, this 5th day of May, 1924:.

CORNELIS BOL. 

